Eur. Phys. J. D 64, 27-35 (2011)
https://doi.org/10.1140/epjd/e2011-10519-4

Regular Article

The structures and properties of FeSi_n/FeSi$\begin{array}{}\mathrm{+}\\ \mathrm{n}\end{array}$/FeSi$\begin{array}{}\mathrm{-}\\ \mathrm{n}\end{array}$ (n = 1 ~ 8) clusters

School of Chemistry and Environment, South China Normal University, Guangzhou 510006, Guangdong, P.R. China

^a e-mail: glli@scnu.edu.cn
^b e-mail: hychen@scnu.edu.cn

Received: 17 September 2010
Received in final form: 14 March 2011
Published online: 27 July 2011

Abstract

The geometry, stability, and electronic properties of iron-doped silicon clusters FeSi_n/FeSi$\begin{array}{}\mathrm{+}\\ \mathit{n}\end{array}$/FeSi$\begin{array}{}\mathrm{-}\\ \mathit{n}\end{array}$ (n = 1 ~ 8) have been systematically investigated using the density functional theory (DFT) approach at the B3LYP/6-311+G* level. Our results show that the ground state structures of FeSi_n/FeSi$\begin{array}{}\mathrm{+}\\ \mathit{n}\end{array}$/FeSi$\begin{array}{}\mathrm{-}\\ \mathit{n}\end{array}$ change from planar to three-dimensional for n > 3. Bipyramidal structures, or their face-capped isomers, are favored for the larger clusters. For neutral FeSi_n clusters, their ground state structures are the trigonal, tetragonal, capped tetragonal, capped pentagonal, and combined tetragonal bipyramids for n = 4 ~ 8, respectively. The lowest-energy structures of the anionic FeSi$\begin{array}{}\mathrm{-}\\ \mathit{n}\end{array}$ clusters essentially retain similar frameworks to their neutral counterparts, while those of the cationic FeSi$\begin{array}{}\mathrm{+}\\ \mathit{n}\end{array}$ clusters are significantly deformed; this is confirmed by their calculated ionization potential and electronic affinity values. For most of the stable structures, the spin electronic configurations are s = 1 or 2 for neutral FeSi_n, s = 3/2 or 5/2 for ionic FeSi$\begin{array}{}\mathrm{+}\\ \mathit{n}\end{array}$/FeSi$\begin{array}{}\mathrm{-}\\ \mathit{n}\end{array}$. The average binding energy values generally increase with increasing cluster size, indicating the clusters can continue to gain energy during the growth process. Fragmentation and second-order energy peaks (maxima) are found at n = 2, 5, and 7 for FeSi_n/FeSi$\begin{array}{}\mathrm{-}\\ \mathit{n}\end{array}$, n = 4 and 6 for FeSi$\begin{array}{}\mathrm{+}\\ \mathit{n}\end{array}$, suggesting that these clusters possess higher relative stability. Furthermore, the HOMO-LUMO gap values show that anionic FeSi$\begin{array}{}\mathrm{-}\\ \mathit{n}\end{array}$ have greater chemical reactivity than cationic FeSi$\begin{array}{}\mathrm{+}\\ \mathit{n}\end{array}$ and neutral FeSi_n, except when n = 7.